On 17 September 2005, New Zealanders will vote for a new government. It will be the fourth time they have voted for a government under the MMP electoral system.
The MMP ("Mixed Member Proportional") electoral system gives each voter two votes – a party vote and an electorate vote. The party votes determine how many parliamentary seats from a total of 120 seats are allocated to each party. Every voter belongs to an electorate, and electorate votes are used to vote for a choice of electorate MP within each electorate. The electorate MPs are somewhat equivalent to the electorate MPs that New Zealanders voted for in their old "First Past the Post" (FPP) electoral system. There are 69 electorates, so there have to be 69 electorate MPs.
The 69 electorate MPs and the 120 party MPs are not separate sets of MPs. 120 is intended to be the total number of MPs, which means that the 69 electorate MPs must be a subset of the 120.
The remaining 51 MPs are chosen from party lists. Each party provides a list of candidates who will be chosen to make up the difference between the party's allocation of seats according to the party vote and the number of electoral seats won by candidates belonging to that party. Each party list is ordered, and successful candidates for each party are chosen from the top of the list.
We can think of electorate MPs as replacing hypothetical list MPs. For example, if party X receives 25% of the vote, they will have 30 MPs in parliament. If there were no electorate MPs, then the first 30 members of party X's party list would become MPs. But if party X also has 25 successful electorate MPs, then those 25 electorate MPs replace 25 of the list candidates, leaving just the top 5 list candidates to receive seats.
One danger with MMP is that voters can become confused about the relative importance of party votes and electorate votes. An electorate vote for a candidate from your favourite party seems like a vote for both the candidate and the party. A party vote for your party seems like a vote for a list candidate. A list candidate is someone that has been chosen for you by someone else. The electorate candidate is someone that you can vote for directly. A voter choosing between electoral candidates will consider personal qualities; a voter choosing between parties will be more interested in policies. For this reason, electorate candidates will probably have better personal qualities, and this makes them seem more important than list candidates. Which makes the electorate vote seem more important than the party vote. But, it is the total numbers of MPs from the different parties that determine which party (or coalition of parties) becomes the government.
In the old FPP system, a vote for your electorate candidate was both a vote for the candidate and a vote for the party. That was twelve years ago, but old habits may die hard.
There's enough confusion on the subject that the New Zealand Electoral Commission conducts polls to determine the public's understanding of how MMP works, and to see if this understanding improves or gets worse over time.
From the point of view of party choice, the party vote counts as a party vote, and the electorate vote has no net effect. The electorate vote can be regarded as a combination of a positive vote for an electorate candidate and a negative vote against a corresponding list candidate for the same party, i.e. the list candidate who will lose their seat if the electorate candidate wins theirs. If we count the party vote as +1 vote and the electorate vote as a combination of +1 and -1, then the total number of party votes per voter comes to +1 + (+1 + -1) = +1.
This voting "equation" depends on the assumption that a successful electorate candidate replaces one corresponding list candidate. But there may be no list candidate to replace. This can happen if the number of MPs for a party as determined by the party vote is less than the number of electorate MPs for that party. It can also happen when an independent candidate wins an electorate seat. An independent candidate has no party (by definition), so their corresponding party vote is always zero.
If the number of electoral seats won by a party is more than the number of seats allocated to that party according to their share of party vote, the excess of electoral seats is called overhang. The rule for dealing with overhang in New Zealand's MMP system is to increase the total number of seats by the size of the overhang, giving each party that has an overhang its correct number of electorate seats, while continuing to give other parties the same proportion of the original 120 seats as determined by party votes.
What is the maximum number of seats that can be created by overhang? You can find out by visiting the official MMP seat allocation calculator. First, pick a party, and enter "100" as their percentage of the party vote. Then pick a different party, and enter "69" as their number of electorate MPs. Finally, press the "Calculate parliamentary seats!" button. You should see a result of "Total MPs" = 189.
Unfortunately the calculator has no options for selecting independent MPs, but you can simulate them by deeming one of the "Other Party" rows to be a party called "Independents", remembering to award them no more than 0% of the party vote.
If you are a New Zealand voter and your electorate vote contributes to an overhang, then the "-1" in your +1 + (+1 + -1) party votes has disappeared, and you are left with +1 + +1 = +2 votes. In other words, you have effectively doubled your number of party votes.
Assuming that many people would vote twice if they could do so legally, one might expect to see a lot of voting for overhang candidates and a lot of overhang MPs. But this isn't the case, at least not in New Zealand. In the history of MMP elections in New Zealand, there has never been an overhang MP, not even an independent overhang MP, and the number of seats won in each MMP election has always been exactly 120. There have been MPs who have changed party allegiance after being voted in, but that's a different story.
So what's going on? Does no one understand that they can double their party vote? Does everyone understand the possibility, but they feel it would be cheating to take advantage of it?
One problem, if you are a voter who has no qualms about "cheating" in this way, is that there has to be a potential overhang candidate to vote for. If all the good electoral candidates belong to parties that expect to receive a significant party vote, then the remaining choice of candidates may be of such poor quality that you wouldn't vote for them, not even for the sake of doubling your vote.
Overhang voting would be more attractive if the parties themselves made some effort to assist those voters wishing to maximise the impact of their votes. For example:
If a party tries too blatantly to manipulate the system, then that might count against it. But in the whole history of democracy, has there ever been a case where voters in an election decided not to vote for their preferred candidates, just because the system was corrupted in favour of those candidates? Not that I know of, but readers might know of some illuminating counter-example. (In most election boycotts, the election is boycotted by the group of voters that expects to lose the elections. The boycott is usually presented as a protest, either against the circumstances in which the election is conducted, or against the unfairness of the power distribution that the election has been designed to create.)
So the question remains, do New Zealanders really understand their own electoral system? And if they do, why aren't they all doubling their votes and voting for overhang MPs, and why haven't we got 189 MPs sitting in parliament? Is it just a matter of time?
The September election has come and gone, and the results have finally come through (after about a week of counting extra votes etc.). This time there was an overhang, for the first time in New Zealand MMP electoral history, consisting of 4 members of the Maori Party voted to the 4 Maori electorate seats, who exceeded by 1 seat the 3 seats that they were entitled to according to their share of the party vote. (An important detail, which I did not mention above, is that you have to win at least 1 electoral seat for any of your party votes to count if your party vote share is less than 5%.)
Of the successful Maori Party candidates, Tariana Turia and Pita Sharples were numbers 1 and 2 respectively on the Maori Party's party list, Te Ururoa Flavell was number 10, and Hone Harawira wasn't on the party list at all. We can't really say which of these 4 counts as the "overhang MP", because if any one of them had lost their electoral seat and the other three had won, and the Maori Party's share of the party vote had been the same, then the loser would not have been entitled to a seat, and there would have been no overhang.
I could attempt to discuss the subtle details of New Zealand's political landscape that led to this result, but I won't, because I don't want to get mired in discussing political issues that I don't particularly understand better than anyone else, and the main intention of this article was just to look at theoretical issues of voting strategy.